Weird Stuff!

sometimes, completely randomly it seems, i start to drive i put it into 1st and start to accelerate and i get hardly any response, the car sorta sputters like its going to die then it acts normally again. this happens rarely but its very odd and i would like to know what the problem is.

also often times i accelerate through 1st and shift to 2nd and start to accelerate and the car accelerates for a little bit then sorta flatens out then accelerates a bit more then flattens off and it does this through the lower rpms or 2nd gear. whats wrong?!?